Generally, grippers refer to apparatuses which apply physical force or pressure to a target to hold it. Grippers are typically used in transfer systems. Particularly, pin-type grippers are mainly used to transfer targets made of soft material such as fabric, porous material, rubber, etc.
Referring to FIG. 1, a conventional pin-type gripper 1 includes two cylinders 3a and 3b which are installed in a housing 2 and are oriented to be inclined downwards in directions crossing each other. A plurality of pins 6a and 6b are respectively provided on ends of the piston rods 4a and 4b of the cylinders 3a and 3b by mounting blocks 5a and 5b. The pins 6a and 6b are oriented at predetermined inclination angles θ such that they cross each other.
In this conventional construction, when the rods 4a and 4b are extracted by the operation of the cylinders 3a and 3b, the pins 6a and 6b protrude downwards from the bottom of the housing 2 and extend to the left and the right. In this way, the pins 6a and 6b are obliquely pegged into the surface of a target P, thus making it possible to hold the target P and transfer it using the pin-type gripper 1.
The pin-type gripper can be effectively used to transfer a target made of soft material. However, because the conventional pin-type gripper uses two cylinders, the following problems arise.
First, the structure of the gripper is complex, and the size of the gripper, including the housing, is excessively large.
Second, a special and detailed design for controlling the two cylinders at the same time is required, resulting in a high possibility of malfunction or error.
Third, consequentially, a lot of time and effort are required to manufacture and operate the gripper.